Last Updated on May 13, 2020 by Sagar Aryal
Rapid Diagnostic Test vs Real-Time PCR (qPCR)
There are several diagnostic tests that have been authorized for Emergency Use by the FDA for diagnosis of a wide range of infections. Notably, these diagnostic tests aim at identifying an infected individual from a non-infected person, using different working principles and duration for the tests vary. Diagnostic tests can be molecular-based or immuno-assays.
The most common tests are:
Rapid Diagnostic tests
- They are mainly serological tests principally working to detect immune reactive elements i.e antibodies or detecting the pathogenic antigens.
- They are mainly used for screening of diseases, and at a health care worker’s convinces hence, the are point-of-care diagnostic tests
Real-Time PCR (qPCR)
- This is a molecular-based technique that principally works to qualitatively detect the presence of pathogen genome i.e RNA or DNA.
- The genome undergoes different stages of processing before identification followed by sequencing for classification of the pathogen strains.
Differences between the Rapid Diagnostic Test and Real-Time PCR (qPCR)
Features | Rapid Diagnostic Test | Real-Time PCR (qPCR) |
| Sample | They require whole blood or plasma or serum samples for tests or biopsy. | The test uses liquid or solid samples depending on the condition of the test e.g Respiratory infection requires nasal swabs or nasopharyngeal swabs. |
| Principle | Qualitative and semi-qualitative in-vitro devices. | Qualitative and quantitative in-vitro medical devices. |
| Types | Rapid Antibody test Rapid Antigen test | quantitative real-time PCR semi-quantitative real-time PCR |
| Objectivity | The test aims at identifying and/or detecting antibodies, majorly IgG and/or IgM. OR Detection of antigens (pathogen particles ) in blood. | The test aims at amplifying and detecting the pathogen genome (RNA and DNA). |
| Duration of Test | It takes approximately 15 minutes to 2 hours to get the test result. | It can take 1 hour to 48 hours to get the test result. |
| Reagents | The test uses a solution buffer to allow the capillary tube. | Several PCR reagents are used. |
| Instrumentation | It is a simple chromatographic capillary tube. | It is complex with several compartments each performing a series of protocols. |
| Procedure | Most are one-step procedures. | They involved a series of steps including denaturation, annealing, and extension. |
| Platforms | Lateral flow tests Agglutination Dipstick Microfluidics | High-throughput platforms which include Dynamic Array Chip, TaqMan Open array, and SmartChip. |
| Sensitivity and specificity | Most have high sensitivity >95% and specificity of >99%. | The sensitivity of most tests ranges from >95% and specificity of >83%. |
| Applications | – Used for preliminary or emergency medical screening. – Used in point-of-care testing for diagnosis. – Used for diagnosis of a wide range of diseases including Malaria, HIV, TB, Influenza, Dengue fever, Strep B, Syphilis, COVID-19. | – Research Applications – Genetic cloning – Genetic disease diagnosis – Cancer detection
|
| Results | A positive test indicates the presence of Antibodies against the specific pathogen or presence of antigens of the pathogen. A negative test indicates the absence of antibodies produced against the pathogen or absence of pathogenic antigens. | Positive results indicate the detection of pathogen genome RNA/DNA and negative results indicate a lack of RNA/DNA genome. |
| Portability and Cost | They are small and easily portable and inexpensive. | Most are large machines difficult to move from one place to another and they are expensive to manufacture and purchase. |
| Examples | Rapid HIV Test Rapid Plasma Reagin Rapid Influenza Diagnostic Test Malaria Antigen Detection Test Rapid Strep B Test Rapid Urease test Rapid Dengue test Syphilis Rapid Test Tuberculosis IgM/IgG Rapid test | COVID-19 RT-qPCR Influenza Real-Time PCR Parasitic Real-Time PCR Fungal Real-Time PCR Bacterial Real-Time PCR |
References and Sources
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1860455/
- https://www.researchgate.net/figure/The-relationship-between-rapid-diagnostic-test-RDT-and-polymerase-chain-reaction-PCR_fig2_285595052
- https://www.intechopen.com/books/polymerase-chain-reaction-for-biomedical-applications/high-throughput-platforms-in-real-time-pcr-and-applications
- https://www.indiatvnews.com/news/india/real-time-pcr-test-vs-anti-body-test-what-is-india-s-coronavirus-testing-strategy-608900
- https://www.indiatoday.in/india/story/how-rapid-antibody-tests-are-different-from-existing-pcr-tests-for-covid-19-explained-1663441-2020-04-05